Short circuiter for repulsioninduction electric motors



April 4, 1950 J. LEFLAR SHORT cmcuxma FOR REPULSION-INDUCTION ELECTRIC MOTORS Filed Oct. 30, 1944 INVENTOR.

ATTORNEY Patented Apr. 4, 1950 SHORT CIRCUITER FOR REPULSION- INDUCTION ELECTRIC MOTORS Jerome Leflar, Dayton, Ohio, assignor to The Master Electric Company, Dayton, Ohio, a corporation of Ohio Application October 30, 1944, Serial No. 560,951

8 Claims. 1

This invention pertains to electric motors and more particularly to a centrifugally operated short circuiter or operation changing device for automatically converting an alternating current motor of the repulsion-induction type from a repulsion-starting condition to an induction-run ning condition, and vice versa, in accordance with fluctuations of speed of rotation of the armature.

The object of the invention is to improve the construction as well as the mode of operation of centrifugally operated short circuiters, whereby they may not only be economically manufactured, but will be more eflicient in use. automatic in operation, uniform in action, have relatively few operating parts, and be unlikely to get out of repair.

A further object of the invention is to provide a compact quick acting unit which is responsive to relatively small fluctuations of speed, and which possesses definition of movement or snap action into and out of operative position.

A further object of the invention is to provide a floating type of contact element having minimum frictional resistance to movement under centrifugal influence or upon cessation thereof.

A further object of the invention is to provide a short circuiting device having the advantageous structural features and inherent meritorious characteristics and mode of operation hereinafter set forth.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation, or their equivalents, as hereinafter described, or illustrated in the accompanying drawings.

Referring to the accompanying drawings,

Fig. 1 is a side elevation of an electric motor commutator partly broken away, showing applied thereto a short circuiter device embodying the present invention.

Fig. 2 is an end elevation thereof, also partly broken away.

Fig. 3 is an enlarged detail view.

Like parts are indicated by similar characters of reference throughout the several views.

The electric motor, per se, forms no part of the present it "ention and has not been illustrated. Centrifugally actuated short circuiters for the present purpose have been long and well known. However, the present short circuiting unit has been designed to overcome some inherent defects and obviate disadvantages of prior art devices of analogous character, and is applicable to repulsion-induction motors of various detail construction or specific design.

It has been found that while prior art short circuiting devices operate quite satisfactorily when incorporated in relatively slow speed motors they are not sufficiently sensitive and responsive to minute fluctuations of centrifugal influence when operating at high speed. The present short circuiter construction is especially desirable for use with reversible motors, especially when quick reversal is required. Ordinarily repulsion induction motors while operating under induction influence cannot be reversed until upon retardation of speed the short circuiting unit has changed the motor to repulsion condition of operation, which due to lag of the short circuiter elements necessitates considerable delay. The present construction is such that the short circuiter con tact elements respond quickly to a relatively slight speed decrease permitting prompt return to repulsion operating condition when reversal may be effected, and the contact elements again respond quickly to speed acceleration to restore the motor to induction running condition.

Referring to the drawings l indicates the rotor shaft on which is mounted a conventional commutator comprising a core 2 about the periphery of which are disposed a continuous succession of commutator bars 3 electrically insulated from the core 2 and from each other by interposed strata 4 of insulating material. The ends of the commutator bars 3 project in overhanging relation beyond the face of the core 2.

Located also upon the rotor shaft 1' closely adjacent to the commutator is the short circuiting unit forming the subject matter hereof which includes a hub 5 which extends within the recess of the commutator formed by the overhanging ends of the commutator bars 3 and is peripherally rabbeted at 5. At the outer side of the hub 5 is a peripherally flanged disc or cup I of electro conductive material, the flange of which forms a support and a fulcrum for a plurality of centrifugally responsive oscillatory contact arms 8. The arms 8 are flat and relatively light weight and are positioned close together. The contact arms are formed with hook shaped terminals 9 engageable over the marginal flange of the disc or cup I. The arms are also provided at mid length with arcuate seats i fl to receive an endless helical garter spring l 2 common to the assembly of contact arms.

Normally the contraction of the annular spring ll retracts the several arms 8 into seating engagement with the outer face of the disc or cup I and with the periphery of the hub t beneath the overhanging commuator bars In this position the arms 8 bridge the recess formed by the rabbet t in the hub and the adjacent flanged disc 1. As the speed of rotation increases the contact arms t tend to move bodily outwardly against the yielding resistance of the retractile spring ii until the inturned ends to of the arms 8 engage with the inner side of the flange lot of the disc '5'. Continued. bodily movement of arms 8 being thus arrested the arms tend to oscillate under centrifugal influence against the yield ing resistance of the spring ii. in. such con-- tinuing movement the arms t fulcrum at by engagement of the inturned ends oi the arms with the flange of the disc "5!, until such out-- ward oscillation is arrested by the contact engagement or the inner ends of the arms S with the inner sides of the overhan ing ends commutator The disc '3 being oi conductive mate. ll and common to all of the arms which are therevnth, the con act engagement of the opposite ends of the arms with the commutator bars electrically interconnects bar of entire serie: of com-- mutator bars with the common ctro-ccnductive disc 5 and through said with all companion commutator bars.

To protect the assembly or contact from injury or displacement a housing disc l con toured to overhang and enclose the contact and retractile spring is unted on the hub closely adjacent to the disc electro-conductive disc and housing disc i in a peripheral rabbet ll? of The jeoting portion is displaced by timing or st in ing at iii to secure the "i and in their assembled relation.

In practice the short circuiting r'iit is ordinarily completely assembled apart fro the motor and is subsequently positio upon the rotor shaft 5 in contiguous relation with the usual commutator.

By the present construction pivotal connections of the arms and the in nt frictional resistance thereof to oscillation or the contact arms is entirely eliminated. l? rther, the ireedom of movement or floating character of the contact arms not only inirimizes friction, but affords a capability for slight motion of the contact arms relative to the supporting flange and the overhanging commutator bars, whereby there be sufficient rubbing or wiping action thereon to keep the contact surfaces clean thus insure good electrical connection, The contact arms possess two definite movements or stages of action, a bodily movement outwardly by which the interned extremity of the hoot: shaped terminal of the contact arm is made to contact the common conductor and a sub sequent oscillatory moti n about a point of con tact on the flange until the free end or" the con," tact engages the commutator. In the latter movement as the arm finds its seat on the commutator bars, the hooked terminal thereof is free for slight adjusting motion to accommodate the opposite end of the arm oi the commutator.

From the above description it will be apparent that there is thus provided a device of the char-- acter described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the electro of the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in. language more or less specific as to structural features, it is to he understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A light weight short circuiting device for a repulsion induction electric motor commutator having overhanging commutator bars, said short circuiting device being responsive to minute variations in speed of the commutator, including a cylindrical mounting flange in fixed parallel ally spaced relation with the commutator, an a: ruler series of axially elongated parallel. re oscillatory contact arms having hook. shaped said arms subject to centrifugal in and 's posed with their hooked ends in tracldle relat: n. with mounting flange, and their opposite ends extending into overlapping interiorly spaced relation with the overhanging commutator bars, an annular retractile spring surrounding the annular series or conarms against the yielding resistance of which the arms are bodily movable in radial direction until the heel: ends thereof contact the inner periphery of the mounting flange Where:- upon the contact bars effect further oscillatory movement under continuing centrifugal influence against the yielding resistance of the annular spring about a contact point of the hook. shaped end of each bar on the flange until the opposite ends of the arms make snort circuiting contact with the overhanging commutator bars and their osci atory motion is limited thereb 2. A light weight short ircui device for electric motor commutators, said device being responsive to minute variations in speed of the commutator, including a fixed mounting hub, an axially extending flange thereon or electro-conductive material, an annular series of aiially elongated independent hook. shaped contact arms disposed about said flange with the hook per tions thereof extending in spaced relation nte orly of the ilange and opposite ends thereof projecting in overlapping relation with the flange into proximate relation with commutator bars, annular retractile :5 'ng surroundthe series of contact arms against which the arms are radially movable under centrifugal in rluence into contact relation of the hook portion thereof with the interior the flange be yond which they are capable of further oscillatory motion against the yielding resistance of the spring about the point of contact of the hook portion of each arm the nterior of the flange into short circ contact with the commutator bars.

3. A light weight short eircuiting device for eorninutators, said device h 'ng onsive to minute variations in the commutator, inc an. electro-conductive flange fixed in concentric axially spaced relation witl tl C0l1i mutator, an annular series of axially hook shaped contact arms disposed the with their hook shaped portions in straddle relation with the e and their opposite ends extending into proximate relation flu about with the commutator, and an annular retractile spring surrounding the annular series of contact arms against the yielding resistance of which the contact arms are capable of an initial radial movement under centrifugal influence, into contact engagement of the hool: portions of the arms with the interior of the fiange and of subsequent oscillatory motion into short circuiting contact with the commutator about contact points of the hook portions with the interior of said flange.

4. A light weight short circuiting device for commutators, said device bein responsive to minute variations in speed of the commutator, including a cylindrical flange fixed in concentric axially spaced relation with the commutator, an annular series of axially elongated centriiugally actuated contact elements disposed in overlying relation to the flange with one end of each element normally extending interiorly of the flange in spaced relation therewith, and the other end of each element extending into proximate spaced relation with the commutator bar, and an annular retractile spring surrounding the series of contact elements against the yielding resistance of which the elements are bodily movable into contact engagement of one end of each of the elements with the interior of the flange and the other ends of the elements into short circuiting contact engagement with the commutator.

5. A light weight short circuiting device for commutators, said device being responsive to minute variations in the speed of the commutator, including a. cylindrical flange disposed in concentric axially spaced relation with a commutator to be short oircuited, an annular series of axially elongated centrifugally actuated contact arms disposed with one end of each arm normally extending in spaced relation within the flange for fulcrum engagement therewith, and the other ends of the arms extending into proximate relation with the commutator for short circuiting engagement therewith, and an annular retractile spring surrounding the series of contact arms at a point intermediate the flange and commutator against the yielding resistance of which the arms are movable, said point being such that under centrifugal influence the arms initially move into iulcruming engagement with the flange and subsequently into short circuiting engagement with the commutator.

6. A light Weight short circuiting device for commutators, said device being responsive to minute variations in the speed of the commutator, including a series of separate contact arms radially movable under centrifugal influence, the mass of the individual arms being substantially evenly distributed throughout the area thereof, an annular restraining member normally surrounding in relatively spaced relation the terminals of the arms at one end thereof, the opposite ends of the arms projecting into spaced relation with the commutator, and retractile means surrounding the arms at a point in axially spaced relation with the ends thereof against the yielding resistance of which the contact arms are movable under centrifugal influence, said point being such that the arms are initially movable until the terminals at one end thereof make fulcruming engagement with the restraining member about which fulcrum the arms are capable of further oscillatory motion into short circuiting engagement of the opposite ends thereof with the commutator.

7. A contact element for a short circuiter for commutators, comprising an axially elongated light Weight substantially balanced arm the opposite margins of which are parallel, and a terminal big-ht formed at one end thereof for spaced straddle engagement with a restraining member.

8. A short circuiter for commutators, including an annular series of substantially J-shaped arms having their mass substantially equally distributed throughout their total area, a relatively fixed annular restraining member over which the terminal bights of the J-shaped contact arms are engageable in relatively spaced straddle relation, and relative to which the bights of the arms are radially movable under centrifugal influence into contact relation therewith, and wherein the arms fulcrum upon said annular member during further oscillatory motion of the arms about their contact points with the annular member into short circuiting contact engagement of the opposite ends of the arms with the commutator, and resilient retractive means disposed intermediate the contact points of said arms in axially spaced relation therewith against the yielding resistance of which the arms are movable under centrifugal influence successively into fulcrum engagement with the annular restraining member and subsequently into short cirlcuiting engagement with the commutator.

JEROME LEFLAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,640,900 Larsh Aug. 30, 1927 1,666,457 Leland Apr. 17, 1928 1,684,941 Bullivant Sept. 18, 1928 1,709,415 Swift Apr. 16, 1929 1,723,010 Brump Aug. 6, 1929 1,724,547 Ballman Aug. 13, 1929 2,130,883 Hartog Sept. 20, 1938 2,126,342 Nippert 1- Aug. 9, 1938 2,206,045 Okun July 2, 1940 

